Composite Interlayer Research Articles

A novel method for strengthening C/C composite joint with high entropy alloy/Ni composite interlayers by spark plasma sintering: In-situ synthesis of high entropy cermet joint structure

C/C composite was successfully brazed with TiZrHfTa/Ni or ZrHfNbTa/Ni composite interlayers using spark plasma sintering. The influence of different interlayers and joining parameters on the joint morphology, shear strength at room temperature and 1000 °C was investigated. For both composite interlayers, the C/C joints obtained at 1800 °C for 30 min consisted of a single high entropy cermet structure, with a near equimolar high entropy carbide hard phase and a near pure Ni binder phase. However, the use of different composite interlayers resulted in differences in the elastic modulus and hardness of the formed high entropy carbide phase. The maximum shear strengths of the obtained C/C composite joints using TiZrHfTa/Ni and ZrHfNbTa/Ni interlayers at room temperature were close, with value of 37.49 ± 1.44 MPa and 38.95 ± 1.26 MPa, respectively. Because (Zr-Hf-Nb-Ta)C had better high-temperature stability than (Ti-Zr-Hf-Ta)C, the obtained C/C-ZrHfNbTa/Ni-C/C joint exhibited a higher shear strength of 28.54 ± 1.71 MPa at 1000 °C. After shear testing at both room temperature and 1000 °C, fractures in all joints predominantly occurred within the C/C composite near the reaction layer, indicating a substrate failure mode. The use of composite interlayers resulted in C/C composite joints with excellent shear strength, primarily due to the in-situ synthesized high entropy cermet reaction layer, which provided superior strength and toughness. Additionally, the laser-textured pattern on the C/C composite surface formed numerous interlocking structures at the joint interface, further enhancing the joints' shear strength.

Research on the Strengthening Mechanism of MWCNTs-Cuf Composite Interlayer for Si3N4/TC4 Brazed Joints

With the rapid development of aerospace technology, the high-quality brazing connection between Si3N4 ceramic and TC4 titanium alloy has become a key factor in advancing the development of aircraft antenna covers. To improve the mechanical strength of the joints, this study used the electrophoretic deposition method to prepare a multi-walled carbon nanotubes-foam copper (MWCNTs-Cuf) composite interlayer and selected the optimal deposition parameters. The most suitable brazing parameters under this interlayer were also determined. The joints’ formation mechanism and fracture mode were revealed to elucidate the synergistic strengthening mechanism of the composite interlayer. The results showed that MWCNTs, based on their phase characteristics, produced high-density dislocations and fine crystal strengthening effects during the brazing cooling process. This effectively resisted the corrosion of the brazing material on the foam copper (Cuf), protected the integrity of the foam copper framework, and exerted the excellent plastic deformation ability of foam copper (Cuf). It reduced the residual stress in the joints, resulting in the highest shear strength of the MWCNTs- Cuf composite interlayer, reaching 96.23 MPa. Compared with only adding Ag-Cu-Ti active brazing filler metal and adding ordinary foam copper interlayer, the shear strength increased by 78.2% and 44.7%, respectively.

Ultrastrong and ductile superalloy joints bonded with a novel composite interlayer modified by high entropy alloy

Diffusion bonding (DB) with interlayers is sought-after for manufacturing high-performance turbine disks of powder metallurgy (PM) superalloys with precise and intricate inner cavity structures. Developing novel interlayer materials is challenging but crucial for enhancing bonding quality and joint properties. We designed a multi-interlayer composite bonding (MICB) method, employing sandwich-structured interlayers of “BNi2/high entropy alloy (HEA)/BNi2”, to join a PM superalloy FGH98. The MICB joint exhibited an ultrahigh shear strength of ∼1132 MPa and exceptional ductility, indicating a typical ductile fracture pattern with numerous dimples. Owing to the introduction of liquid BNi2 interlayer, initial bonding interfaces were eliminated and replaced by newborn grain boundaries (GBs), preventing brittle interfacial fracture. Due to the diffusion of Al/Ti/Ta from the base metals (BMs), massive ordered γ' nanoparticles also precipitated in the joint. Moreover, the addition of HEA foil reduced the stacking fault energy (SFE) of the joint and facilitated the formation of deformation twins (DTs). Thus, during the deformation process, the γ' nanoparticles, and multiple substructures like stacking faults (SFs), Lomer-Cottrell (L-C) locks, DTs, and 9R phases enhanced the work-hardening capability and strengthened the joint. Simultaneously, the multiplication and interaction of DTs induced a softening mechanism of dynamic recrystallization (DRX) during the entire deformation process and dominated when the plastic instability occurred, resulting in numerous adiabatic shear bands (ASBs) consisting of γ/γ' nano-bands, which indicates a significant improvement of the joint ductility.

Tribological Properties of Multilayer DLC/MoS2 Nanocomposite Coatings on Microtextured Titanium Alloy Surfaces

Single surface texture or coating technology is gradually unable to produce lasting lubrication of a TC4 titanium alloy in a harsh environment. In order to address this problem, a rectangular microstructure is prepared on the surface of a TC4 titanium alloy by laser processing, and then MoS2/DLC composite interlayer nanocoatings are prepared on the surface by non-equilibrium magnetron sputtering. Friction and wear tests are then carried out on single fabricated, coated and fabricated coatings. The results show that the MoS2/DLC composite interlayered nanocoating can effectively combine with the texture to achieve better friction reduction compared with the single texture and coating. The textured composite coating has the lowest friction coefficient (reduced from 0.4122 to 0.0978) and wear. Through controlled experiments, the textured coating showed good tribological properties at different temperatures and in different friction cycle tests. This study can effectively improve the tribological properties of metal materials through composite coatings, providing research ideas for enhancing the service life of alloys under long-term friction in high-temperature environments.

Application and research of three-dimensional composite fiber interlayer in lithium-sulfur battery

Lithium-sulfur (Li-S) batteries are regarded to be the most probable‌ electrochemical energy storage devices for large-scale applications because of their high energy and green characteristics. Nevertheless, the polysulfides generated during the cycle of Li-S batteries can cause the "shuttle effect", reducing the utilization rate of sulfur (S) and electrochemical performance. In this study, a novel three-dimensional composite fiber (TDCF) interlayer was prepared and placed between the S cathode and the PP separator to adsorb polysulfide and restrain the "shuttle effect". The results show that the capacity retention rate of Li-S battery is still higher 3:50 ratio, 200 ml of anhydrous ethanol was added to moisten, than 70 % after 200 charge-discharge cycles at 1 C.

Synergistic Reduction and Oxidation Resistant Interface Modifier for High‐Voltage and High‐Loading Solid‐State Lithium Batteries

AbstractSolid‐state batteries (SSBs) with high‐voltage cathodes and Li‐anodes offer promising energy density and safety for next‐generation batteries. However, poor contact and electrochemical instability of solid electrolyte interfaces hinder their long‐term performance. Traditional rigid solidification interlayers possess restricted capability to address these issues. Herein, a composite buffer interlayer (CBI) with localized high‐concentration electrolytes (LHCEs) in a flexible polymer scaffold, tackling contact and stability problems and ensuring a perfect interface is developed. The extended electrochemical window provides it with synergistic antioxidation and antireduction capabilities, making it compatible with high‐voltage cathodes and Li anodes, while an in situ formed LiF‐Li3N rich inorganic interface ensures uniform lithium deposition and prevents dendrite formation. This CBI enables lithium symmetric cells to achieve a super high critical current density of 7.2 mA cm−2. Most impressively, coupled with a high‐voltage LiNi0.83Co0.12Mn0.05O2 cathode (NCM83), the full cell achieves 94.1% capacity retention after 125 cycles (coulombic efficiency >99.8%) at a mass loading of 14.6 mg cm−2 and a high voltage of 4.45 V. Additionally, a pouch cell with 17.2 mg cm−2 NCM83 achieves an initial discharge capacity of 3.82 mAh cm−2 an superior cycling stability (75 cycles, 89% capacity retention), showcasing the practical potential of LHCE‐CBI enabled SSBs.

Microstructure and performance of compositionally graded Ta2O5/Ti thin films on Ti6Al4V alloy deposited by magnetron sputtering

Tantalum pentoxide (Ta2O5) ceramic is a promising material for modifying metal implants due to its superior wear resistance, chemical stability, and biocompatibility. However, the clinical application of Ta2O5 coatings may be limited by inadequate adhesion, resulting from performance mismatches between Ta2O5 coatings and metal substrates. In this study, a Ta2O5/Ti gradient film was developed on the Ti6Al4V titanium alloy substrate using magnetron sputtering, consisting of a Ti bonding layer, four Ta2O5-Ti composite interlayers with graded composition, and a Ta2O5 surface layer. The microstructure and properties of the Ta2O5/Ti gradient films were investigated, with a Ta2O5 monolayer coating as a reference. Results reveal that the gradient layers have higher density, lower surface roughness, diminished residual thermal stress, and improved adhesion, mechanical properties, and wear resistance compared to the Ta2O5 monolayer coating. However, the corrosion resistance of the Ta2O5/Ti gradient layer sample is inferior to that of the Ta2O5 monolayer coating sample, attributed to interphase corrosion between Ta2O5 and Ti within the interlayers. These significant findings offer a promising approach for enhancing the overall performance of Ta2O5 coating on Ti6Al4V titanium alloy surfaces, thereby opening avenues for widespread application in the biomedical industry.

A novel method for reducing the brazing temperature of C/C composite with TiZrHfTa/Ni composite interlayers

C/C composite was successfully brazed with TiZrHfTa/Ni composite interlayers at lower temperature far below the melting point of TiZrHfTa refractory high entropy alloy. The influence of brazing parameters on the joint morphology, indentation fraction toughness of the reaction layer, shear strength at room temperature and at 1000 °C, and fracture behavior was investigated. The results show that all of the C/C composite joints contained two main phases: an equimolar (Ti-Zr-Hf-Ta)C hard phase and a near-pure Ni binder phase. The maximum indentation fracture toughness of the obtained joint reaction layer material was 15.52 ± 0.64 MPa·m1/2. This was proved to be beneficial to improve the strength and toughness of the joint. Meanwhile, the maximum shear strengths of C/C-TiZrHfTa/Ni-C/C joint at room temperature and at 1000 °C reached 33.24 ± 1.85 MPa and 21.70 ± 2.12 MPa, respectively. Abundant slip lines, in-situ dimples, and tearing ridges resulting from Ni plastic deformation suggest a predominantly ductile fracture mode in the joint. This work introduces an innovative method, which can not only ensure the service of C/C composite in high temperature environment, but also effectively reduce the joining temperature.

A Bifunctional Carbon-LiNO3 Composite Interlayer for Stable Lithium Metal Powder Electrodes as High Energy Density Anode Material in Lithium Batteries

Lithium metal remains a promising candidate for high-energy-density rechargeable batteries due to its exceptional specific capacity and low reduction potential. However, practical implementation of lithium metal anodes faces challenges such as dendrite formation, limited cycle life, and safety concerns. This study introduces a novel approach to enhance the performance of lithium metal powder (LMP)-based electrodes by embedding a LiNO3-carbon composite interlayer between the LMP electrode and the copper foil current collector. The N-rich carbon interlayer acts as a reservoir for LiNO3, enabling its gradual release to maintain prolonged stability of the interfacial reactions of the Li-metal and providing additional Li nucleation sites. Our findings demonstrate that the LiNO3-carbon composite effectively suppresses dendrite formation, improves reversible capacity, and stabilizes the solid electrolyte interphase. Additionally, we validated the fast-charging capabilities of the Li/NCM622 half-cell employing the LiNO3-carbon-coated Cu foil with LMP electrodes. Our results highlight the significant synergistic effect of the LiNO3 additive and carbon interlayer in enhancing the performance of lithium metal-based batteries.

A novel high entropy composite interlayer for diffusion bonding of TC4 titanium alloy to 316L stainless steel

Titanium/steel hybrid structure exhibit broad prospects in the nuclear industry and aerospace applications. Achieving high-performance titanium/steel bonding is crucial. Herein, the novel AlCoCrNiCuAg/Cu high entropy composite interlayer was designed for vacuum diffusion bonding of TC4 alloy to 316L stainless steel. The effects of bonding temperature, holding time and assembly sequence on the interfacial microstructure and mechanical properties were investigated, and the fracture behaviors were researched. Typical microstructure of the joint bonded at 1010 °C for 90 min via AlCoCrNiCuAg/Cu sequence was TC4/β-Ti/β-Ti+TiFe/TiFe2+χ+σ/α-Fe+χ+σ/316L. With bonding temperature increased, due to the dispersed distribution of the Cuss phase in the Ti-Fe phases, the highest shear strength of 222.8 MPa was achieved at 1010 °C/90 min. The cleavage characteristics were confirmed in the fracture surfaces, suggesting the brittle fracture. The main cracks were located at the junction of the TiFe2+χ+σ and the β-Ti+TiFe layers, further confirmed that the interface appeared immense strain, accelerating the joint fracture.

All-Solid-State Lithium-Sulfur Batteries of High Cycling Stability and Rate Capability Enabled by a Self-Lithiated Sn-C Interlayer.

All-solid-state lithium-sulfur batteries (ASSLSBs) have attracted intense interest due to their high theoretical energy density and intrinsic safety. However, constructing durable lithium (Li) metal anodes with high cycling efficiency in ASSLSBs remains challenging due to poor interface stability. Here, a compositionally stable, self-lithiated tin (Sn)-carbon (C) composite interlayer (LSCI) between Li anode and solid-state electrolyte (SSE), capable of homogenizing Li-ion transport across the interlayer, mitigating decomposition of SSE, and enhancing electrochemical/structural stability of interface, is developed for ASSLSBs. The LSCI-mediated Li metal anode enables stable Li plating/stripping over 7000h without Li dendrite penetration. The ASSLSBs equipped with LSCI thus exhibit excellent cycling stability of over 300 cycles (capacity retention of ≈80%) under low applied pressure (<8MPa) and demonstrate improved rate capability even at 3C. The enhanced electrochemical performance and corresponding insights of the designed LSCI broaden the spectrum of advanced interlayers for interface manipulation, advancing the practical application of ASSLSBs.

Improvement of Joint Strength of TC4/AZ91D Bimetal in Solid-liquid Compound Casting Process Using Cu-Ni Composite Interlayer

Improvement of Joint Strength of TC4/AZ91D Bimetal in Solid-liquid Compound Casting Process Using Cu-Ni Composite Interlayer

Electrophoretic deposition of CNTs on a Cu foam interlayer for enhancing Cf/SiC–Nb brazed joint performance

The high residual stress and low toughness of ceramic matrix composite/metallic brazed joints poses severe challenges for the stable operation of high-speed aircraft under harsh conditions. This article innovatively tackles this issue with electrophoretic deposition (EPD), creating a CNT covered Cu foam composite interlayer for brazing Cf/SiC and Nb with an Ag–Cu–Ti alloy filler. A layer of mass ratio-controllable and percolated CNTs was physically adsorbed on the surface of the Cu foam substrate. EPD time was systematically investigated for its impact on the microstructure and mechanical properties of the joints. Results indicate that during brazing, the CNTs reacted with the active Ti element, transforming into ultrafine TiC grains with particle sizes ranging from 6 to 16 nm. These were dispersed evenly in the Ag solid solution. The elastic recovery rate of the cluster regions showed an increase of 123 % compared to the Ag solid solution, showing improved toughness of the seam. When the EPD time was 80 min, the shear strength of the joint produced with the composite interlayer reached 128.6 MPa, a 69 % increase over the directly brazed joint. Moreover, the fracture location of the joint shifted from the brazed seam towards the interior of the bulk Cf/SiC. Additionally, finite element analysis was utilized to confirm a significant decrease in residual stresses within the joint, and verified the findings.

Harnessing Liquid Metals with In Situ Polymerized Electrolyte for Anode‐Free Lithium Metal Batteries

AbstractTo enhance safety and energy density in conventional Li‐ion batteries, anode‐free or zero‐lithium configurations using only a current collector (CC) in the anode have emerged. However, challenges including rapid Li dendrite growth, low Coulombic efficiency, safety concerns, and thickness issues hinder the practical use of anode‐free batteries (AFBs) with liquid electrolytes (LEs) or solid electrolytes (SEs). Herein, potential AFBs using an anode current collector coated with a liquid metal (LM)@C nanocomposite with an in situ polymerized electrolyte (PE) are reported. Interestingly, LM nanoparticles added to the composite layer on CC play a crucial role in promoting uniform Li plating/stripping behavior through a self‐healing mechanism, along with reversible liquid–solid–liquid phase transitions caused by alloying and de‐alloying of Li and LMs. Furthermore, incorporating in situ polymerized electrolytes stabilizes LMs by preventing the agglomeration of LM nanoparticles, resulting in significantly improved cell performance compared to other conventional LEs. A systematical model study with ex situ analysis unveils the synergetic effects between LMs and PE, along with elucidating the mechanism of in situ polymerization and Li‐LMs reactions. The investigation contributes valuable insights for future studies on practical applications of AFBs using polymer electrolytes and composite interlayers.

Chemical Prelithiated 3D Lithiophilic/-Phobic Interlayer Enables Long-Term Li Plating/Stripping.

The up-to-date lifespan of zero-excess lithium (Li) metal batteries is limited to a few dozen cycles due to irreversible Li-ion loss caused by interfacial reactions during cycling. Herein, a chemical prelithiated composite interlayer, made of lithiophilic silver (Ag) and lithiophobic copper (Cu) in a 3D porous carbon fiber matrix, is applied on a planar Cu current collector to regulate Li plating and stripping and prevent undesired reactions. The Li-rich surface coating of lithium oxide (Li2O), lithium carboxylate (RCO2Li), lithium carbonates (ROCO2Li), and lithium hydride (LiH) is formed by soaking and directly heating the interlayer in n-butyllithium hexane solution. Although only a thin coating of ∼10 nm is created, it effectively regulates the ionic and electronic conductivity of the interlayer via these surface compounds and reduces defect sites by reactions of n-butyllithium with heteroatoms in the carbon fibers during formation. The spontaneously formed lithiophilic-lithiophobic gradient across individual carbon fiber provides homogeneous Li-ion deposition, preventing concentrated Li deposition. The porous structure of the composite interlayer eliminates the built-in stress upon Li deposition, and the anisotropically distributed carbon fibers enable uniform charge compensation. These features synergistically minimize the side reactions and compensate for Li-ion loss while cycling. The prepared zero-excess Li metal batteries could be cycled 300 times at 1.17 C with negligible capacity fading.

Converting an O-vacancy-rich oxide into a multifunctional separator modifier for long-lifespan lithium metal batteries

The lithium metal anode is hailed as the desired “holy grail” for the forthcoming generation of high-energy-density batteries, given its astounding theoretical capacity and low potential. Nonetheless, the formation and growth of dendrites seriously compromise battery life and safety. Herein, an yttria-stabilized bismuth oxide (YSB) layer is fabricated on the polypropylene (PP) separator, where YSB reacts with Li anode in-situ in the cell to form a multi-component composite interlayer consisting of Li3Bi, Li2O, and Y2O3. The interlayer can function not only as a redistributor to regulate Li+ distribution but also as an anion adsorber to increase the Li+ transference number from 0.37 to 0.79 for suppressing dendrite nucleation and growth. Consequently, compared with the cell with a baseline separator, those with modified separators exhibit prolonged lifespan in both Li/Li symmetrical cells and Li/Cu half-cells. Notably, the full cells coupled with ultrahigh-loading LiFePO4 display an excellent cycling performance of 1700 cycles with a high capacity retention of ∼80% at 1 C, exhibiting great potential for practical applications. This work provides a feasible and effective new strategy for separator modification towards building a much-anticipated dendrite-free Li anode and realizing long-lifespan lithium metal batteries.

Inter-layer failure and toughening mechanisms of carbon/aramid hybrid fiber composites interleaved with micro/nano pulps under low-velocity impact load

Hybrid fiber-reinforced polymer (HFRP) composites are widely used in aerospace structures because of their excellent overall performance. However, it is still challenging to address the issue of high sensitivity to delamination between dissimilar material interlayers in HFRP composites. This study combines experimental and numerical simulation to analyze the low-velocity impact behavior and interlaminar damage of two types of HFRP. Based on a micromechanical model, an equivalent aramid pulp (eAP) toughening laminate model is developed. The impact behavior of the HFRP toughen by eAP only in dissimilar material interlayers is simulated based on the model. The effect of eAP areal density on the impact behavior and evolution of interlaminar damage is analyzed. Results show that the maximum force and impact stiffness of eAP-toughened HFRP increase initially with the increase in eAP areal density, and then decrease slowly. The area and extent of damage of dissimilar material interlayers in eAP toughened laminates is significantly reduced. Finally, the interlaminar toughening and failure mechanisms by eAP-toughening only in dissimilar material interlayers of the HFRP composites are systematically revealed from fiber bridging and damage transfer perspectives.

Achieving ultrafine grain strengthening Cf/SiC-GH3536 joints brazed with Cu-Ti-WC composite interlayer via cold spray additive manufacturing

Cold spray additive manufacturing (CSAM), as a solid-phase additive manufacturing technology, exhibits enormous potential in the fabrication of metal matrix composite. The conventional preparation methods of composite filler often have some problems, such as agglomeration of reinforcements and poor fluidity, which have limited the further application of composite filler. In this study, we proposed a novel method to prepare the Cu-Ti-WC composite interlayer for brazing Cf/SiC and GH3536 using CSAM. The synergistic deposition mechanism of matrix particles and reinforcing particles in the composite interlayer was revealed. The deformation and recrystallisation of Cu and Ti particles and the crushing and tamping of WC particles achieved the deposition of the cold sprayed Cu-Ti-WC interlayer. The CSAM achieved a tight bonding of the composite filler, generating the initial TiC before reaching the brazing temperature. And the Fe-W-Ni-Cr-Cu multi-principal element alloys (MPEA) generated from the reaction between WC and Cr(s,s), and formed ultrafine grain regions (∼200 nm) with [2–1 −1 0]HCP-MPEA // [0 0 1]TiC and [-1 1 1]FCC-MPEA // [1 1 3]TiC orientation due to the hindering effect of the increased TiC. The shear strength of Cf/SiC-GH3536 joint brazed with cold sprayed Cu-Ti-WC interlayer was improved to 112.0 MPa, which is 1.5 times higher than that of Cu-Ti-WC powder filler. This study shows the great potential of CSAM in fabricating metal-based composite interlayers for brazing and aids in composite-metal joining for higher performance.

Vinyl-based interlayers synthesized by variable pulsed plasma for polymer composites

The low-pressure pulsed plasma is a crucial tool for the construction of materials in the form of coatings with variable properties. The pulsed mode is characterized by many parameters such as pulse on-time, off-time, pulse period, pulse frequency, duty cycle, and using the total power, the average power during the pulse can be introduced as the effective power. Based on a pulse period ranging from 2 to 100 ms and a total power of 10–500 W, it is demonstrated that the effective power is the key parameter responsible for the properties of the synthesized coatings independent of the total power. When an organosilicon precursor with a vinyl functional group, this parameter allows the chemical and physical properties of vinyl-based coatings to be controlled over a wide range, allowing to optimize their properties as functional interlayers in polymer composites to control their performance.

Unraveling the Mechanisms of Zirconium Metal–Organic Frameworks‐Based Mixed‐Matrix Membranes Preventing Polysulfide Shuttling

Lithium–sulfur batteries are considered as promising candidates for next‐generation energy storage devices for grid applications due to their high theoretical energy density. However, the inevitable shuttle effect of lithium polysulfides and/or dendrite growth of Li metal anodes hinder their commercial viability. Herein, the microporous Zr fumarate metal–organic framework (MOF)‐801(Zr) is considered to produce thin (≈15.6 μm, ≈1 mg cm2) mixed‐matrix membranes (MMM) as a novel interlayer for Li–S batteries. It is found that the MOF‐801(Zr)/C/PVDF‐HFP composite interlayer facilitates Li+ ions diffusion, and anchors polysulfides while promoting their redox conversion effectively. It is demonstrated that MOF‐801 effectively trapped polysulfides at the cathode side, and confirmed for the first time the nature of the interaction between the adsorbed polysulfides and the host framework, through a combination of solid‐state nuclear magnetic resonance and molecular dynamics simulations. The incorporation of MOF‐801(Zr)/C/PVDF‐HFP MMM interlayer results in a notable enhancement in the initial capacity of Li–S batteries up to 1110 mA h g−1. Moreover, even after 50 cycles, a specific capacity of 880 mA h g−1 is delivered.